What happens if you use a class that is not defined in the manifests directory?

When you attempt to use a class that is not defined in the manifests directory, Puppet will raise an error indicating that it cannot find the class you are trying to include or declare. This behavior is crucial as it helps maintain the integrity and reliability of your Puppet configurations.

Puppet relies on a well-defined structure and expects all referenced classes to be explicitly defined in the manifests. If you reference a class that does not exist, Puppet cannot apply the desired state because it does not have the necessary instructions to execute. This mechanism ensures that you are alerted to potential issues in your code during the compilation phase before any changes are actually attempted on the target systems.

The options suggesting that the class would be ignored, work without issues, or automatically defined do not align with Puppet's design principles, which prioritize error handling and clear, defined configurations. This focus on error detection is part of what makes Puppet a powerful tool for configuration management, ensuring that users explicitly manage and declare their infrastructure.